Reactor distribution apparatus and quench zone mixing apparatus

ABSTRACT

A quench zone mixing apparatus ( 16 ) that occupies a low vertical height and has an improved mixing efficiency and fluid distribution across the catalyst surface includes a swirl chamber ( 20 ), a rough distribution network ( 100 ), and a distribution apparatus ( 120 ). In the swirl chamber ( 20 ), reactant fluid from a catalyst bed above is thoroughly mixed with a quench fluid by a swirling action. The mixed fluids exit the swirl chamber ( 20 ) through an aperture to the rough distribution system ( 100 ) where the fluids are radially distributed outward across the vessel to the distribution apparatus ( 120 ). The distribution apparatus ( 120 ) includes a plate ( 122 ) with a number of bubble caps ( 130 ) and associated a drip trace ( 150 ) that multiply the liquid drip stream from the bubble caps ( 130 ) to further symmetrically distribute the fluids across the catalyst surface. Alternatively, deflector baffles may be associated with the bubble caps ( 130 ) to provide a wider and more uniform liquid distribution below the plate ( 122 ). The distribution apparatus ( 120 ) can be used in the reaction vessel ( 10 ) without the swirl chamber ( 20 ) and rough distribution system ( 100 ), e.g., at the top of a vessel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of a application Ser. No. 08/659,122,filed Jun. 4, 1996, now U.S. Pat. No. 5,989,502.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a distribution apparatus and a quenchzone mixing apparatus (or device) that may include the distributionapparatus, both of which are suitable for efficiently mixing andredistributing reactants across the horizontal cross-section of avertical reaction vessel.

2. Discussion of Related Art

Many catalytic processes are carried out in reactors that contain aseries of separated catalytic beds. Frequently, in such processes,quench zone mixing devices are advantageously located to provide rapidand efficient mixing of the fluid streams being processed in the reactorwith a cooler fluid stream supplied from an external source.Consequently, the temperature of the process stream entering thesuccessive catalyst beds can be controlled. One skilled in the art willappreciate that the better the mixing of the reactant streams, thebetter the temperature and reaction can be controlled. As a result, theoverall performance of the reactor will be better.

Examples of quench zone mixing devices include U.S. Pat. No. 3,353,924,U.S. Pat. No. 3,480,407, U.S. Pat. No. 3,541,000, U.S. Pat. No.4,669,890, and U.S. Pat. No. 5,152,967. Some of these devices arecomplicated and are prone to plugging. Others need a relatively largevertical space to ensure the desired degree of mixing. Still otherscreate an undesirably high pressure drop. Consequently, there is acontinuing need for a suitable quench zone mixing device that canefficiently mix fluid streams in a low vertical space with an acceptablylow pressure drop.

Typically, the quench zone mixing devices are located above anassociated fluid distribution system; for example, a horizontallydisposed distribution plate or tray. The distribution plate collects thefluid (vapor and liquid), uniformly distributes it across the plate anddischarges the fluid on to the catalyst bed. Such distribution tray maycontain a number of “bubble cap” assemblies which may be disposed overone or more openings in the distribution tray. The bubble cap providesintimate mixing of the vapor and liquid before the mixed phase fluid isdistributed across the catalyst bed.

Examples of distribution trays include U.S. Pat. No. 2,778,621, U.S.Pat. No. 3,218,249, U.S. Pat. No. 4,960,571, U.S. Pat. No. 4,836,989,U.S. Pat. No. 5,045,247, U.S. Pat. No. 5,158,714 and U.S. Pat. No.5,403,561. Although one or more of these designs may be acceptable,there is still room for improvement, particularly in providing a uniformdistribution of vapor and liquid phases into contact with the catalystin the reactor vessel.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a distribution apparatusthat includes a redistribution tray (also referred to herein as a“redistribution plate”). It is another object of the invention toprovide a quench zone mixing apparatus (also referred to herein as the“quench zone mixing device”) that includes a swirl chamber, a roughdistribution network disposed underneath the swirl chamber, and,preferably, a distribution apparatus disposed underneath the roughdistribution network. It is to be understood that the distributionapparatus can be associated with the quench zone mixing device or can beused separately from the quench zone mixing device; for example, at thetop of the reactor vessel.

The distribution apparatus includes a redistribution plate (alsoreferred to herein as a “plate”) having a plurality of apertures and aplurality of bubble caps with at least some of the bubble capsassociated with at least some of the apertures. In one embodiment, aplurality of drip trays are substantially horizontally disposedunderneath the redistribution plate. At least some of the drip trays areassociated with at least some of the bubble caps. The drip trays receivefluids exiting the associated bubble caps and distribute them through atleast one discharge port provided on the bottom of the drip tray. Inanother embodiment, the drip trays have at least two discharge ports tomultiply the fluid drip stream received from the bubble cap andsymmetrically distribute the fluid across the catalyst surface.

Instead of the drip trays, at least one deflector baffle, and preferablya plurality of deflector baffles, may be placed below the redistributiontray. Preferably at least some of the deflector baffles are associatedwith at least some of the bubble caps.

As noted above, the quench zone mixing apparatus includes a swirlchamber. The swirl chamber is adapted to receive fluids from upstream inthe reactor (such as those exiting a catalyst bed located above theswirl chamber). Preferably, the swirl chamber is substantiallycylindrical. The swirl chamber includes a wall disposed between aceiling and a floor. The wall has a plurality of openings, such as inletopenings, that provide a means of fluid communication into the swirlchamber. The floor surrounds an orifice, which provides a means forfluid to exit the swirl chamber. Preferably, a weir is provided aboutthe periphery of the orifice. Baffles are located inside the swirlchamber which stabilize the vapor and liquid phase vortices, reduce therequired overall height of the swirl chamber, provide a wide operatingrange for vapor and liquid throughput, and promote turbulence/mixingwithin each of the fluid phases. At least some of the openings have abaffle associated with the openings.

The rough distribution network is disposed beneath the swirl chamber toreceive fluids from the swirl chamber. The rough distribution networkincludes a splash plate and radially outwardly extending channels. Thesplash plate is adapted to collect fluids from the swirl chamber andradially outwardly distribute them through the channels. Preferably, thechannels include side walls with spaced apart notches to allow fluid toexit the channels. Fluids exiting the channels fall onto a distributionapparatus disposed beneath the rough distribution network.

Preferably, the distribution apparatus includes the redistribution platesubstantially horizontally mounted below the rough distribution networkand the swirl chamber. The redistribution plate extends substantiallyacross the entire cross-section of the vessel to separate an uppersection of the vessel from a lower section. The redistribution platecomprises a plurality of apertures and a plurality of bubble capsassociated with the apertures of the redistribution plate. Morepreferably, a bubble cap is associated with each aperture to provide thesole means of fluid flow through the plate.

The bubble caps include a riser and a spaced apart cap. The riser has atop and a bottom and the riser is secured near the bottom to theredistribution plate. A passageway is defined between the top and bottomand provides a means of fluid communication across the redistributionplate. Preferably, the cap has a plurality of spaced apart slots toallow the flow of fluids through the cap and into the annulus defined bythe cap and the riser.

In a preferred embodiment, the ceiling of the swirl chamber is closed. Aliquid collection tray, preferably frusto-conically shaped, surroundsthe swirl chamber and is sloped so that the one end adjacent the inletopenings is lower than the other end adjacent to the vessel wall. Fluidexiting the preceding catalyst bed falls onto the liquid collection trayor onto the ceiling of the swirl chamber where it is directed onto theliquid collection tray and through the inlet openings. Baffles arelocated inside the swirl chamber adjacent the openings and incommunication with the openings to receive and direct incoming fluidcircumferentially about the swirl chamber. In this preferred embodiment,the orifice is centrally located and provides the sole means for fluidto exit the swirl chamber. Additional baffles, i.e., wall baffles andinternal baffles (the latter located on the floor of the swirl chamber),may also be included.

In another preferred embodiment, a quench fluid system is provided tointroduce quench fluid into or above the swirl chamber. The quench fluidsystem may include a feed pipe in communication with a concentricmanifold that surrounds the swirl chamber. A plurality of quench fluidlaterals in fluid communication with the manifold extend radially inwardand terminate with nozzles that extend into the swirl chamber. Thenozzles are located adjacent and below the baffles and have openings todirect quench fluids into the fluid stream exiting the baffles.

Alternatively, the quench fluid system may include a feed pipe whichintroduces the quench fluid directly (without a manifold) into the swirlchamber or into an area above the swirl chamber.

In another embodiment of the present invention, a reactor is providedwith the quench zone mixing apparatus of the present inventioninterposed between two catalyst beds. Preferably, the quench zone mixingapparatus is supported within a vessel of the reactor by a supportstructure that includes a concentric hub, which may be formed to act asa torsion tube, and at least a first set of radial beams extendingradially outward from the hub and terminating at a support ring that isattached to the reactor vessel wall.

In particular, the radial beams comprise a flange that supports theredistribution tray and a web of the beams preferably includes aplurality of openings to allow the passage of fluids across the vessel.In addition, the webs also carry the channels. The radial beams alsosupport the swirl chamber and, in the area between the wall of the swirlchamber and the vessel wall, the radial beams may have a vertical heightthat slopes downward from the vessel wall to the swirl chamber wall.Specifically, the radial beams at the swirl chamber wall have a verticalheight at about the bottom of the openings on the swirl chamber wall andat the vessel wall the radial beams have a vertical height greater thanat the swirl chamber wall. The liquid collection tray is provided on thetop of the radial beams in the area between the swirl chamber wall andthe vessel wall to create a downwardly sloping conical surface. As inother embodiments, the liquid collection tray is preferablyfrusto-conical shaped and it surrounds the swirl chamber.

Alternatively, a first set of radial beams having a single verticalheight may be provided with a second set of radial beams locatedvertically above the first set. In this case, the top of the second setof radial beams is downwardly sloped in the same fashion as describedabove. In either case, the liquid collection tray collects fluid fromthe ceiling of the swirl chamber and from the catalyst bed above anddirects it through the openings in the swirl chamber.

In a preferred embodiment, a first set of radial beams having a singlevertical height is used to support the swirl chamber and distributionchannels. Additionally, a support ring is attached to the outside wallof the swirl chamber at a location just below the inlet openings. Asecond support ring is attached to the vessel wall at a locationapproximately equal to the elevation of the swirl chamber ceiling. Theliquid collection tray is provided on top of the support rings in thearea between the vessel wall and the swirl chamber to preferably createa frusto-conical shape that directs fluids from the catalyst bed abovetoward the swirl chamber inlet openings. The ring at the wall providessupport for the liquid collection tray and a sealing surface to preventfluids from bypassing the swirl chamber.

The present invention also contemplates an improvement in known quenchzone mixing devices wherein a rough distribution network is interposedbetween a mixing chamber (or a swirl chamber) and a distributionapparatus. The present invention therefore provides a reactor thatincludes the quench zone mixing apparatus of this invention, whichcomprises a mixing chamber and a distribution apparatus. In particular,the improvement comprises a rough distribution network disposed betweenthe mixing chamber and the distribution apparatus, the roughdistribution network comprising a splash plate in fluid communicationwith outwardly extending channels. Preferably, the channels extendoutward radially from the splash plate. The splash plate preferably hasapertures and the channels preferably include side walls with spacedapart notches to allow fluid to exit the channels.

The invention is also directed to a bubble cap which comprises: a riserhaving a lower end located within and extending through an aperture in aplate of the distribution apparatus and a top end to define a passagewaybetween the ends, the passageway including an inlet and an outlet; a caplocated over the top end of the riser, the cap having a top portion anda downwardly extending skirt portion: a spacer located between the riserand the cap to maintain a gap between the top end of the riser and thecap; and a deflector baffle placed below the outlet of the passageway.

The deflector baffle may have any desired construction, and it redirectsthe majority of the fluid flowing downwardly from the riser passageway,so that the fluid forms a relatively wide spray pattern over thedownstream catalyst bed (as compared to the fluid flow pattern from abubble cap without the deflector baffle).

Additionally, the invention is directed to a bubble cap comprising: ariser having a lower end located within and extending through anaperture in the plate of the, distribution apparatus and a top end todefine a passageway between the ends; a cap located over the top end ofthe riser, the cap having a top portion and a downwardly extending skirtportion; at least one spacer located between the riser and the cap tomaintain a gap between the top end of the riser and the cap; and aplurality of riser vanes located between the top end of the riser andthe top portion of the cap. An annulus (“bubble cap annulus”) is createdbetween the riser and the cap. The riser vanes are preferably flushagainst the underside of the bubble cap top wall. The riser vanes arespaced from each other to form vane passageways. Preferably, the vanepassageways are the only (or sole) means of fluid communication betweenthe bubble cap annulus and the riser passageway.

A bubble cap may also include the deflector baffle and the riser vanes.

The deflector baffle and/or the riser vanes (as described herein) mayalso be included in a bubble cap of any other construction.

The present invention also contemplates the use of a distributionapparatus where the distribution apparatus is not associated with thequench zone mixing apparatus i.e., the distribution apparatus is used inaddition to the quench zone mixing apparatus or used in a reactor thatdoes not have a quench zone mixing apparatus. In this embodiment, thedistribution apparatus may be provided above a catalyst bed. Forexample, the distribution apparatus may be provided at the top of thereactor or between successive catalyst beds. The distribution apparatuswill include a redistribution plate and a plurality of bubble caps, asdescribed above. In addition, the distribution apparatus may also beprovided with a plurality of drip trays, as described above. In anotherembodiment, the drip trays may be omitted and at least one deflectorbaffle included in the distribution apparatus, as described above. Theriser vanes may be included in any of the bubble caps. In thisembodiment, the distribution apparatus is usually called a “distributiontray”.

The present invention also contemplates the use of a quench zone mixingapparatus in a process for contacting a first fluid with a second fluid,wherein the first and second fluids may be liquid and/or gas.Preferably, the process occurs in a portion of a reactor between twosuccessive spaced apart beds of particle form solids, e.g., catalystparticles. In one embodiment, the invention broadly includes introducinga first fluid into the reactor: transporting the first fluid through afirst catalyst bed; collecting the reaction product from the firstcatalyst bed and transporting it through the quench zone mixing devicewhere it is further mixed and reacted with a quench fluid (“secondfluid”) to form a further reaction product that is distributed onto thesurface of a second bed, including catalyst particles, locateddownstream from the first catalyst bed. In one particular application ofthis embodiment, hydrotreating and hydrocracking of relatively heavypetroleum hydrocarbon stocks, the first fluid is a hot mixture of gasand liquid and the second fluid is a cold gas or cold liquid.

In a particular embodiment, the process is directed to a two phasedownflow reactor. The process includes introducing a first fluid, suchas liquid and gas reactants, into the reactor at a location above aswirl chamber. Preferably, the first fluid is introduced in an uppersection of the reactor. The first fluid is then introduced into theswirl chamber. A second fluid, e.g., a quench gas, is introduced intothe swirl chamber and contacts the first fluid to form a swirl chamberfluid mixture. The swirl chamber fluid mixture exits the swirl chamberand is collected by a rough distribution network where the swirl chamberfluid mixture is radially distributed over a splash plate and outwardlyextending channels. Subsequently, a fluid mixture exiting the channelsis conducted to a distribution apparatus. The distribution apparatusincludes a redistribution plate with a plurality of apertures and aplurality of bubble caps with at least some of the bubble capsassociated with at least some of the apertures. The fluid mixture istransported through the redistribution plate to form a redistributionplate fluid mixture. The redistribution plate fluid mixture iseventually transported to a downstream section of the reactor.

In one embodiment of the process, a deflector baffle is associated withat least some of the bubble caps. Also, riser vanes may be included inat least some of the bubble caps.

In another embodiment of the process, before the redistribution platefluid mixture is transported to the downstream section of the reactor,it is collected on a plurality of substantially horizontal drip trayswith at least some of the drip trays which are located underneath theplate and associated with at least some of the bubble caps. Thecollected redistribution plate fluid mixture is distributed through atleast one discharge port in the drip trays and some separation of thegas from the liquid takes place on the drip trays.

The invention is also directed to a process for transferring a fluidfrom a first bed of a reactor to a second bed of a reactor, locateddownstream from the first bed. The process comprises introducing a fluidfrom the first bed of the reactor into a swirl chamber. Subsequently,the fluid is removed from the swirl chamber, and is introduced into arough distribution network including a splash plate and outwardlyextending channels. Then, the fluid is conducted from the roughdistribution network to a distribution apparatus, which includes aredistribution plate with a plurality of apertures and a plurality ofbubble caps. At least some of the bubble caps are associated with atleast some of the apertures. The fluid is then transported through theredistribution plate to the second bed of the reactor. The fluid mayinclude a gas, a liquid or a mixture of liquid and gas. A quench fluid,liquid or gas, may also be introduced separately into the swirl chamber.

The invention is also directed to a process for redistributing a fluidwithin a reactor. The process includes collecting the fluid on adistribution apparatus and distributing the fluid to a downstreamsection of the reactor in a substantially even fashion across thecross-section of the reactor. The distribution apparatus includes aredistribution plate with a plurality of apertures and a plurality ofbubble caps, with at least some of the bubble caps associated with atleast some of the apertures. In one embodiment, a plurality ofsubstantially horizontal drip trays are located underneath the plate andassociated with at least some of the bubble caps. Consequently, thefluid is collected on the surface of the redistribution plate andtransported through the plate, to a downstream section of the reactor.If the drip trays are included, the fluid is transported through theplate onto the drip trays where it is transported to a downstreamsection of the reactor. In another embodiment, a deflector baffle isassociated with at least some of the bubble caps. Further, riser vanesmay be included in at least some of the bubble caps.

The invention is also directed to a method of operating a swirl chamberwhich includes: a liquid collection tray; a wall disposed between aceiling and a floor, the floor including an orifice which provides ameans of communication out of the swirl chamber, the wall defining aninside of the swirl chamber; a plurality of openings (also referred toas “inlet openings”), in the wall, which provide a means of fluidcommunication into the swirl chamber; a plurality of baffles (or firstbaffles) located inside the swirl chamber and in communication with theopenings to receive and direct incoming fluid circumferentially aboutthe swirl chamber. The method comprises introducing a fluid into theswirl chamber through the openings and directing the fluid onto thefirst baffles; subsequently, the fluid is directed from the firstbaffles onto the floor and towards the orifice, in such a manner that atleast one of the first baffles is partially submerged by the fluid.

The apparatus and process of the present invention may be particularlyapplicable for use in fixed bed catalytic processing systems forhydrotreating and hydrocracking of relatively heavy petroleumhydrocarbon stocks. Such processing systems may use reactors with one ormore vertically spaced catalyst beds. Although the invention may beparticularly applicable for use in hydrogen treatment of hydrocarbons,the process and apparatus are not limited to such use and can be used inany system where the mixture of a vertically flowing liquid and avertically flowing gas, or a lighter liquid and heavier liquid, isdesired. For example, the invention may also be used in aromaticsaturation, catalytic dewaxing and hydrofinishing operations.

The quench zone mixing apparatus may be placed in any suitable locationin a reactor vessel. For example, it may be placed at the top of thereactor, so that any fluid entering the reactor will contact the quenchzone mixing apparatus before it contacts any other internal reactordevices. Alternatively, the quench zone mixing apparatus may be placeddownstream from any internal reactor devices, such as internal catalystbeds.

For purposes of exemplification and illustration, a range of parametersis given below for some specific processing systems for hydrotreatingand hydrocracking relatively heavy petroleum hydrocarbon stocks in whichthe apparatus and process of the present invention can be used. Suchprocessing systems typically use reactors having inside diameters of 5to 20 feet with about 2 to 5 vertically spaced catalyst bed spaces withlengths of 5 to 50 feet, and use catalysts typically having particlesizes of {fraction (1/32)} inch to ¼ inch.

As pointed out in greater detail below, the quench zone mixing apparatusof this invention provides important advantages. The design of theinvention apparatus minimizes the overall vertical height of the quenchzone mixing apparatus. As a result, the overall vertical height of thereaction vessel can be decreased, thereby reducing the capital cost ofthe vessel. At the same time, intimate mixing and thermal equilibrationis achieved while maintaining only a moderate pressure drop across thedevice.

The term “fluid” as used in the specification and claims is meant toinclude both liquids and gases. The term “vapor” and “gas” are usedinterchangeably herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a multi-bed catalytic reactor with a portion cut away toshow a vertical section view of a portion of the distribution apparatusand the quench zone mixing apparatus of the present invention.

FIG. 2 is a perspective view of a portion of the quench zone mixing anddistribution apparatus with several portions removed to better show thedetail of the apparatus. It is understood that the portion of the quenchzone mixing apparatus not shown is radially symmetrical to the portionshown.

FIG. 2A is a perspective view of a portion of the quench zone mixing anddistribution apparatus showing a different embodiment of portions of thequench zone mixing apparatus. Several portions have been removed tobetter show the detail of the apparatus.

FIG. 2B is a perspective view of a portion of the quench zone mixing anddistribution apparatus showing yet another different embodiment ofportions of the quench zone mixing apparatus. Several portions have beenremoved to better show the detail of the apparatus.

FIG. 2C is a perspective view of a portion of the quench zone mixing anddistribution apparatus showing a different embodiment of the apparatus.Several portions have been removed to better show the detail of theapparatus.

FIG. 2D is an end view of a radial support beam and distribution channelof the rough distribution network of the embodiment of FIG. 2C.

FIG. 2E is a perspective view of a portion of the liquid collectiontray, which includes an alternative design of the tray.

FIG. 2F is a schematic illustration of the top view of the liquidcollection tray 78, including a portion thereof formed of integratedcollection tray baffles.

FIG. 2G is a schematic illustration of a portion of the liquidcollection tray 78, which includes integrated collection tray baffles ofan alternative construction.

FIG. 3 is a perspective view of a portion of the swirl chamber of thequench zone mixing apparatus with several portions removed to show thedetail of the swirl chamber. It is understood that the portion of theswirl chamber not shown is radially symmetrical to the portion shown.

FIG. 3A is a side view of an alternative embodiment of the underflowbaffle 42B.

FIG. 4A is a top view of a portion of the quench zone mixing apparatusto show the quench fluid system. It is understood that the portion ofthe quench fluid system not shown is radially symmetrical to the portionshown.

FIG. 4B is a cross-sectional view of a portion of the quench fluidsystem.

FIG. 4C is a schematic illustration of an alternative embodiment of theintroduction of a quench fluid (or other fluid) into the circumferentialbaffle opening in the swirl chamber.

FIG. 4D is a cross-section of the swirl chamber illustrating analternative placement of the quench fluid piping.

FIG. 4E is a cross-section of the swirl chamber illustrating yet anotheralternative placement of the quench fluid piping.

FIG. 5A is top view of a portion of the quench zone mixing apparatus toshow further detail of the rough distribution network. It is understoodthat the portion not shown is radially symmetrical to the portion shown.

FIG. 5B is a partial cross-sectional view of a portion of the quenchzone mixing apparatus to show further detail of the distributionchannels and redistribution tray. It is understood that the portion notshown is radially symmetrical to the portion shown.

FIG. 5C is an end view of a radial support beam and distribution channelof the rough distribution network.

FIG. 6A is a perspective view of the redistribution tray used in thedistribution apparatus of the present invention. For clarity, many ofthe individual bubble caps are not shown.

FIG. 6B is a perspective view of an individual bubble cap associatedwith an aperture of the redistribution tray of FIG. 6A and with its driptray. Portions are cut-away to show the detail of the bubble cap anddrip tray.

FIG. 7 is a perspective view of an alternative embodiment of the driptray as shown in FIG. 6B illustrating a plurality of drip guides.

FIG. 8 is a perspective view of an alternative embodiment of the driptray shown in FIG. 6B illustrating an alternative bottom construction.

FIG. 9 is a perspective view of an alternative embodiment of the driptray that may be useful in the apparatus of the present invention.

FIG. 10 is a cross-sectional view of an alternative embodiment of abubble cap.

FIG. 11 is a top elevation view of the bubble cap taken along the viewline 11—11 of FIG. 10.

FIG. 12 is a schematical perspective view of a portion of the bubble capof FIG. 10.

FIG. 13 is a cross-sectional view of a bubble cap with an alternativedeflector baffle.

FIG. 14 is a top view of an alternative embodiment of a deflectorbaffle.

FIG. 15 is a top view of yet another alternative embodiment of adeflector baffle.

FIG. 16 is a cross-sectional view of an embodiment of a bubble caphaving riser vanes.

FIG. 17 is a top view of a section of the FIG. 16 bubble cap taken alongthe view line 17—17 of FIG. 16.

FIG. 18 is a cut-away view of an embodiment of a bubble cap including analternative design of riser vanes.

FIG. 19 is top view of a section of the FIG. 18 bubble cap taken alongthe view line 19—19.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT

The quench zone mixing apparatus invention will now be described withreference to its use in a multi-bed, catalytic reactor in which theapparatus is located in a zone between two catalytic beds. It isunderstood by one skilled in the art that the apparatus of the presentinvention can also be used in non-catalytic vessels or reactors.

As shown in FIG. 1, the reactor 10 comprises a cylindrical vessel. Whilethe vessel is preferably substantially cylindrical, it can also have anyshape that is suitable for manufacturing concerns. The vessel istypically constructed of corrosion resistant metal or an equivalentmaterial such as stainless steel, weld overlayed chrome alloy steels, orthe like. The vessel is normally insulated internally or externally foroperation at elevated temperatures.

Typically, an inlet 12 is provided in the vessel at its top portion forconvenience in filling the vessel with catalyst, for routinemaintenance, or for flow of fluid, as dictated by the particularapplication. An outlet 14 is provided in the vessel at its bottomportion to permit the discharge of the fluid product. Fluid quench istypically admitted to the vessel through a side wall nozzle 13 connectedto a quench feed pipe. Alternatively, quench fluid may be introducedthrough the top or bottom of the reactor.

A cut-away portion 17 illustrates a partial vertical section view of thedistribution apparatus and the quench zone mixing apparatus. Interposedbetween one or more successive catalyst beds is the quench zone mixingapparatus 16 of the present invention. The apparatus includes a swirlchamber 20, a rough distribution network 100 and, preferably adistribution apparatus 120.

The swirl chamber 20 receives and mixes a quench fluid, typically froman external source, with a reactant process fluid stream (“processfluid”, “process stream” or “reactant fluid”) exiting from the catalystbed above. The quench fluid may have a temperature different from theprocess fluid and may be introduced to control the temperature of theprocess fluid. The quench fluid may also be added to adjust thecomposition of the process stream.

The rough distribution network (or system) 100 collects a product streamfrom the swirl chamber (“swirl chamber product stream”) and radiallyoutwardly distributes it to the distribution apparatus. The distributionapparatus 120 includes a redistribution plate 122 (or a plate 122), anumber of bubble caps 130, and a number of associated drip trays 150.When the distribution apparatus is a part of the quench zone mixingapparatus, the distribution apparatus collects the fluid from the roughdistribution system and the swirl chamber. The fluid is then furthermixed by mutual entrainment of the gas and liquid in the bubble caps.The fluid stream exiting the bubble caps is subdivided by the drip traysassociated with individual bubble caps to provide a substantiallysymmetrical and uniform flow distribution of fluid across the catalystsurface.

As also shown in FIG. 1, the distribution apparatus 120 described aboveneed not be associated with the quench zone mixing apparatus but may beprovided in the reactor, e.g. near the top of the reactor to provide foruniform flow distribution to a downstream section of the reactor. Whenthe distribution apparatus is provided in this manner, it will collectfluid from above, further mix the fluid, and uniformly distribute thefluid.

Referring now to FIG. 2, a portion of the quench zone mixing apparatusof the present invention is shown. The apparatus fills substantially theentire cross-section of the vessel and is supported by a supportstructure 60. The support structure has the shape of a wagon wheel witha central hub and radial support beams as spokes. The entire structureis supported in the reactor by a single support ring 62, secured to theinside of the vessel wall by welding, forging or other means. The radialsupport beams lower flanges 70 are notched at the wall end so a web 68of the radial support beams 66 will fit on the support ring. The top ofthe support beam lower flange 70 and the top of the wall support ring 62are at the same elevation to facilitate installation and sealing of theredistribution tray. The support beams can be bolted to positioning lugs(not shown) attached to the wall to provide stability. A central hub 64,concentric with the reactor, may be sized as a manway for maintenance inthe vessel. A first set of radial beams 66 extends radially outward fromthe central hub to the support ring 62. The radial beams 66 have aflange 70 for supporting the redistribution-plate 122. Preferably, eachbeam 66 is I-shaped and its web 68 has a number of openings 72 near theredistribution plate to allow the transverse passage of fluids aroundthe reactor.

The central hub may be constructed of any suitable materials. Forexample, it can be comprised of hub rings 63, as illustrated in FIG. 2B,an annulus 105, which may include internal hub rings, as illustrated inFIG. 2A, or of one or more torsion tubes (each having a cylindricalshape) extending substantially from top to bottom of radial beams (notillustrated in the drawings). If a torsion tube design is used, the endof the support beams is attached to the torsion tube or tubes. Theconstruction of the hub illustrated in FIG. 2 is preferred.

Referring now to FIG. 3, a squat swirl chamber 20 is supported by thesupport structure. Preferably, the swirl chamber is cylindrical. Theswirl chamber has a floor 22 and an orifice 24. Preferably, the floorconsists of a solid plate surrounding a central orifice 24. A round weir26 rises above the orifice 24 to define a shallow basin on the floorinside the swirl chamber. The swirl chamber has a ceiling 28 thatpreferably consists of a solid plate (best seen in FIG. 4B). A sectionof the swirl chamber ceiling and floor may be constructed so that theycan be removed to serve as a manway for maintenance purposes. The sidewall 30 (also referred to herein as the “wall” or “swirl chamber wall”)of the swirl chamber cylinder is solid except for a number of openings32 spaced around the circumference and located just below the ceiling.Preferably, the openings are evenly spaced around the circumference ofthe chamber and have a parallelogram shape and, more preferably arerectangular. Most preferably, the openings are square. In the mostpreferred embodiment, the openings provide the sole means for a fluidfrom an upstream section of the reactor to enter the swirl chamber. Theupstream section of the reactor may include a catalyst bed.

As shown in FIG. 2, a second set of radial beams 74 extends radiallyoutward from the swirl chamber wall toward the reactor wall 11.Preferably, they are located on top of and are fastened to the first setof radial beams 66 to provide a rigid structure. Alternatively, a singlebeam (or a single set of beams) with the same profile as the two beamscould be used (e.g., see FIG. 2C). Throughout the specification, whilespecific reference is made to a second set of radial beams, one skilledin the art will appreciate that a single beam can be equivalently used.The second set of radial beams is taller at the reactor wall than at theswirl chamber. At the swirl chamber wall, the beams have substantiallythe same height as the bottom of the openings on the wall of the swirlchamber. As a result, the top of the second set of beams is downwardlysloped.

In a preferred embodiment shown in FIG. 2A, the second set of radialbeams can be replaced by a first ring 79 attached to the outside wall ofthe swirl chamber adjacent the bottom 34 of the openings 32 and a secondring 77 attached to the reactor wall at a higher elevation than thefirst ring. More preferably, the second ring 77 is attached at anelevation about equal to the ceiling of the swirl chamber. In thisembodiment, the central hub 64 includes an annulus 105, extending fromthe top to the bottom of the hub. The annulus comprises openings 107which enable fluid to flow out to the distribution channels and thenonto the redistribution plate, below the splash plate. The annulus mayinclude internal hub rings (not shown in FIG. 2A). Openings 101 areprovided to allow fluid to flow into or out of the central hub, and toallow for fluid communication between the central and peripheral areasof the redistribution tray. The openings 101 and 107 may have anydesired shape and/or size. Furthermore, the openings 101 may be spaced alarger distance from each other than shown in FIG. 2A. The openings 107may also be spaced a longer distance from each other than shown in FIG.2A. Also, the spacing of the openings 101 and 107 need not be assymmetrical or regular as shown in FIG. 2A. Two adjacent openings may bespaced a larger distance (e.g., several inches), while the nextconsecutive opening may be closely adjacent to the preceding opening. Inthe embodiment of FIG. 2A, elements of the apparatus corresponding tothe elements in other illustrated embodiments are designated by the samereference numbers. The construction and function of various elements ofthe embodiment of FIG. 2A will be apparent to those skilled in the artfrom the discussion of the remaining embodiments.

As will be discussed in more detail below, where two sets of beams areprovided, an opening 76 is provided in the second set of radial beams toallow passage of the quench fluid manifold. Where only a single beam isprovided, an opening is provided in the upper portion of the beam toallow passage of the quench fluid manifold (see FIG. 2C). In thepreferred embodiment having a first and second ring, there is noobstruction for the quench fluid manifold.

A liquid collection tray 78, preferably frusto-conical shaped, is formedby attaching solid plate tray sections (or panels) to the top of thesecond set of radial beams. Of course, if feasible, a single plate maybe fastened to the top of the second set of beams. Of course, where onlya single beam is provided, the tray 78 will be fastened to the top ofthe beam. Similarly, where a first and second ring are provided as inthe preferred embodiment, the outer portion of the tray is fastened tothe second ring while the inner portion is fastened to the first ring.

Since the tray will be sloped, it will form a conical frustum with atrough against the wall of the swirl chamber. Reactants dropping on theliquid collection tray 78 from above flow toward the openings 32 in thewall of the swirl chamber. In the central area of the reactor, reactantsdrop onto the ceiling 28 of the swirl chamber and flow radially outwardover the edge and into the trough. Reactants flow from the trough intothe swirl chamber through the openings. The reactants dropping onto theliquid collection tray and flowing into the swirl chamber include liquidand vapor reactants.

The sloped liquid collection tray reduces the residence time for liquidand vapor on the tray. The reduced residence time consequently reducesthe thermal cracking of the liquid and vapor, coking and the formationof precursors of polynuclear aromatics.

In an alternative embodiment (illustrated in FIG. 2E) at least a portionof the liquid collection tray 78 may be constructed of the solid platetray sections which include(s) ridged sloped panels 78A to furtherreduce the residence time for the fluid, which includes liquid andvapor, on the tray. That is, at least one of the solid plate traysections includes a ridged sloped panel 78A. The ridged sloped panels78A may be placed at any suitable location on the liquid collectiontray. The ridged sloped panels 78A are integrated into the solid platetray sections (or into the single plate). Preferably, the ridged slopedpanels 78A are machined integrally with the solid plate tray sections(or the single plate). The panels 78A would be arranged such that theridge 78B between two adjacent panels would be located radiallysubstantially midway between two respective inlet openings 32. The apexof the ridgeline would be no higher than either the ceiling of the swirlchamber 28 or the point of intersection of the liquid collection tray 78with the reactor wall 11. As such, the ridged sloped panels would norinfluence the overall vertical height required for the installation ofthe quench zone mixing apparatus.

In yet another alternative embodiment, the liquid collection tray 78 maybe constructed with collection tray baffles 78C located (or included) onthe upper surface of the liquid collection tray (FIGS. 2F and 2G). Thecollection tray baffles may be integrated into the liquid collectiontray, e.g., during manufacturing of the liquid collection tray, or theymay be attached to the liquid collection tray after the latter ismanufactured. The collection tray baffles 78C may be of various shapesincluding, but not limited to, flat, V-shaped, scallop shaped andU-shaped. The collection tray baffles are preferably spaced from eachother. The decree of spacing will depend on design criteria.Nonetheless, the collection tray baffles may also be in contact witheach other. FIG. 2F illustrates schematically the liquid collection trayhaving V-shaped collection tray baffles on one of its sections with anopen end of the “V” facing toward the swirl chamber wall 30. FIG. 2Gillustrates schematically a single section of the liquid collection trayhaving U-shaped collection tray baffles with an open end of the “U”facing toward the swirl chamber wall 30. Of course, either any desiredportion(s) of the liquid collection tray or the entire liquid collectiontray may include collection tray baffles. Also, a single liquidcollection tray may include collection tray baffles of different shapeson different solid plate tray sections. The collection tray baffles 78Cpromote mixing of the reactant liquid and/or vapor which has fallen ontothe tray from the catalyst bed above. This mixing will aid in thedissipation of hot zones due to a non-uniform flow through the catalystbed above, e.g. due to channeling. The collection tray baffles 78C wouldtend to increase the residence time for liquid on the tray and,therefore, would preferably be used in lower temperature hydroprocessingapplications having relatively high superficial liquid rates, whereincreased residence time is not detrimental to product quality.Nonetheless, the collection tray baffles may be used in any otherapplications where the apparatus of this invention may be utilized.

FIG. 2B illustrates a perspective view of a portion of the quench zonemixing apparatus showing a modified embodiment thereof. For example, inthe embodiment of FIG. 2B, the size and shape of the openings 72 issomewhat different than in the other embodiments. It will be apparent tothose skilled in the art that, in the embodiment of FIG. 2B, elements ofthe apparatus corresponding to the elements in other illustratedembodiments are designated by the same reference numbers. Theconstruction and function of various elements of the embodiment of FIG.2B will be apparent to those skilled in the art from the discussion ofthe remaining embodiments of the invention.

FIGS. 2C and 2D illustrate a perspective view of a portion of the quenchzone mixing apparatus showing yet another modified embodiment thereof.In this embodiment, a single set of radial beams 66A is used instead ofthe first set of radial beams 66 and the second set of radial beams 74of the embodiment of FIG. 2. In this embodiment, the radial beams 66Ainclude a web 68A. It will be apparent to those skilled in the art that,in the embodiment of FIGS. 2C and 2D, elements of the apparatuscorresponding to the elements in other illustrated embodiments aredesignated by the same reference numbers. The construction and functionof various elements of the embodiment of FIGS. 2C and 2D will beapparent to those skilled in the art from the discussion of theremaining embodiments of the invention.

As best seen in FIG. 3, inside the swirl chamber, baffles 40 areprovided at each opening 32 (also referred to herein as an “inletopening”) to cause the incoming flow to turn 90 degrees or tangent tothe swirl chamber wall so that the fluid flows circumferentiallydownward. Each baffle includes a downwardly angled tangential ramp 42having an edge 44 attached to the wall of the swirl chamber adjacent thebottom 34 of the opening. Preferably, the opening of the ramp into theswirl chamber is substantially rectangular or square with the edge 44 ofone of its sides attached to the swirl chamber wall 30. The opposite ordistal side 46 of the tangential ramp 42 has an impinging wall 48extending upward and joined to an end wall 50 and to an underflow baffle42B that extend substantially normal to the impinging wall. The end wallextends upward from the ramp and one edge 52 of the end wall may beattached to the swirl chamber wall. The impinging wall 48 can be eitherflat or curved parallel to the swirl chamber wall 30. The edge betweenthe impinging wall 48 and the tangential ramp 42 is, in either case,sealed to prevent leakage. The top edges of the impinging wall 48, theunderflow baffle 42B, and the end wall 50 should fit flush against theswirl chamber ceiling to minimize leakage past the baffles. The sideedges of the underflow baffle 42B should fit flush against the swirlchamber wall and the impinging wall 48 to minimize leakage past thebaffles.

In an alternative embodiment, the lower portion of the underflow baffle42C may be curved forward (i.e., in the direction of fluid flow),thereby creating a chute through which the fluids will pass (FIG. 3A).This curvature allows for higher fluid velocities in comparison with asharp-edged underflow baffle, due to reduced viscous energy dissipation.

In another alternative embodiment, at least one additional wall baffle50A and at least one internal baffle 50B, not associated with each inletopening 32, may be incorporated in the design. The wall baffles 50A areattached to the swirl chamber wall 30, extending substantiallyvertically from near the swirl chamber floor 22 to near the swirlchamber ceiling 28. The wall baffles 50A extend radially inward from theswirl chamber wall 30. The wall baffles 50A may be orientedperpendicular to the swirl chamber floor 22 and ceiling 28 or at anyangle to the swirl chamber floor 22 and the ceiling 28, such as that ofthe tangential ramp 42. In one embodiment, internal baffles 50B extendsubstantially vertically from near the swirl chamber floor 22 to nearthe swirl chamber ceiling 28.

Internal baffles 50B are preferably radially oriented, with the sideedges normal to the swirl chamber wall 30, and the weir 26. Internalbaffle 50B may be oriented perpendicular to the swirl chamber floor 22and ceiling 28 or at any angle to the swirl chamber floor 22 and theceiling 28, such as that of the tangential ramp 42.

Internal baffles 50B (and wall baffles 50A) may have any desired size(or shape). Further, some wall baffles 50A may have a different size andshape than other wall baffles 50A. Similarly, some internal baffles 50Bmay have a different size and shape than other internal baffles 50B.Also, not all of the wall baffles 50A and internal baffles 50B have tobe oriented in the same direction (or at the same angle). Some of thewall baffles 50A may be oriented in a different direction and/or at adifferent angle than other wall baffles 50A. Some of the internalbaffles 50B may be oriented in a different direction and/or at adifferent angle than other internal baffles 50B.

The tangential ramp 42 and the impinging wall 48, in conjunction withthe swirl chamber wall 30 and the swirl chamber ceiling 28, thereforedefine a circumferential opening 54. The circumferential opening fromeach baffle (or tangential ramp) is in the same direction, e.g.,counter-clockwise when viewed from above as in FIGS. 2 and 3, to causethe fluid to flow circumferentially, or swirl around the swirl chamber.The circumferential opening may, of course, be positioned in a clockwisedirection, if desired. Exiting the circumferential opening, the vaporand liquid phases of the fluid tend to disengage due to the differencesin their densities. Those skilled in the art will understand that theseparation of the vapor and liquid phases is not complete; thus some ofthe vapor phase may be entrained in the liquid phase and some of theliquid phase may be entrained in the vapor phase. Both phases tend toform vortices, with the vapor phase vortex above that of the liquidphase; the interface between these vortices being designated as the“free surface,” discussed below. The distance from the lower edge 42A ofthe tangential ramp 42 to the floor of the swirl chamber 22 isdimensioned so that, utilizing the inlet pressure drop/velocity head(the latter also referred to as “distance ratio,” both discussed below),at least one of the baffles and, in particular, the impinging wall 48 ofat least one of the baffles, is partially submerged in the swirlingliquid phase vortex. Preferably most or all of the baffles, and, inparticular, the impinging walls 48 of such baffles are partiallysubmerged in the swirling liquid vortex. The term “partially submerged”,as used herein, means that at least some, but not all, of the verticalheight of a particular element (such as the baffles or the impingingwall 48) is submerged in the swirling liquid phase vortex. In thismanner, the impinging wall 48 and the tangential ramp 42 serve as mixingbaffles, which promote turbulence in the swirling vortices. The wallbaffles 50A and internal baffles 50B, if included, also serve as mixingbaffles, which promote turbulence in the swirling vortices. At least oneof the wall baffles 50A and at least one of the internal baffles 50B isalso partially submerged in the swirling liquid vortex. Preferably mostor all of the wall baffles 50A and internal baffles 50B are partiallysubmerged in the swirling liquid vortex. The swirling effect and inducedturbulence ensure good mixing with the other fluid streams from theother tangential ramps. The baffles also reduce the overall verticalheight of the swirl chamber apparatus as they serve to limit theelevation, i.e., the vertical distance above the swirl chamber floor 22,at which the free surface forms. This limiting of the free surfaceelevation also provides the swirl chamber with the flexibility to handlewide variations in liquid and vapor throughput. The ratio of thevertical distance between the lower edge 42A of the tangential ramp 42(FIG. 3) and the swirl chamber floor 22 to the diameter of the swirlchamber (“distance ratio”) is about 0.01 to about 0.30, preferably about0.025 to about 0.25, and most preferably about 0.05 to about 0.2.

In operation, the swirling fluid flows in a spiral manner toward thecenter of the swirl chamber, as it is displaced by additional fluidflowing down the tangential ramps. At the center, the fluid spills overthe weir 26 to exit the swirl chamber. Sufficient pressure drop is takenacross the opening 32, under the underflow baffle 42B, and down thetangential ramp to provide the fluid with enough velocity head toachieve effective mixing in the fluid pool of reactants inside the swirlchamber.

Without wishing to be limited by any theory of operability, it isbelieved that maintaining two parameters within certain limits isimportant to ensure that the impinging wall 48 is partially submerged bythe liquid phase vortex, and that the wall baffle 50A, if used, alsoserves as a mixing baffle. These parameters are: (1) the distance ratio;and (2) the pressure drop across the opening 32. Suitable ranges of thedistance ratio are discussed above. The pressure drop across the opening32 may typically range from about 0.1 psi to about 2.0 psi, and ispreferably less than about 1.0 psi.

The formation of the vapor and liquid phases vortices is desirable andpreferred. While the vortices are not necessary for operating the swirlchamber of this invention, the operation under such conditions where thevortices are not formed is not preferred because it is believed toresult in less than optimum performance of the device.

In reactors where quench fluid is used to cool the reactants or makeup adisappearing reactant, a quench fluid system 80 (best seen in FIGS. 4Aand 4B) may be provided to inject the quench fluid into the swirlchamber. The quench fluid may be from an external source or an internalsource and is generally introduced through a quench feed pipe 82 thatpasses through the vessel wall 11. The quench feed pipe 82 may beconnected to a concentric manifold 84 that passes through the openings76 in the second set of radial support beams (where two sets areprovided) and encircles the swirl chamber 20.

Quench laterals 86 (FIGS. 4A and 4B) communicate with the manifold totransfer the quench fluid to the swirl chamber. The quench laterals 86terminate with nozzles 88 that extend inward through the swirl chamberwall under the tangential ramps. Preferably, the nozzles terminate atabout the innermost portion of the impinging wall 48. (FIG. 3) Thenozzles have an opening 90 to discharge the quench fluid into acorresponding incoming fluid stream flowing down the tangential ramps.The opening 90 may be oriented so that the quench fluid will be directedcircumferentially into the vessel. The nozzles may have a horizontalslot or a number of spaced in-line orifices on the same side as thecircumferential baffle openings 54 to produce flow parallel to thereactants flowing down the ramps. Therefore, the quench fluid mixes withthe swirling reactant fluid flowing beneath the ramp to achieve coolingof the reactant fluid.

Alternately, mixing of the quench fluid with the reactant fluid on theramp may be achieved by orienting the opening 90 to produce flow whichopposes the flow of the fluid exiting the ramp (FIG. 4C). FIG. 4Cschematically illustrates the positioning of the nozzle 88, having anopening 90 (not shown) in the direction opposite to that of the fluidflow from the circumferential opening 54.

Introduction of the quench fluid into the side of the swirl chamber(rather than above) reduces the overall vertical height of theapparatus. Furthermore, allowance does not have to be made for thequench piping between the catalyst support beams and the top of theliquid collection tray. In addition, introduction of the quench fluidinto the swirl chamber promotes the mixing of the fluids. The swirlchamber design therefore achieves excellent liquid—liquid mixing andvapor—vapor mixing of fluids from all sections of the reactor toapproach thermal equilibration. This eliminates hot zone propagationfrom one bed to the next.

In one alternative embodiment, the quench feed pipe 82 may be introducedthrough the bottom of the swirl chamber and extend above the ceiling 28and the liquid collection tray 78. This is illustrated schematically inFIG. 4D. As shown in FIG. 4D, the quench feed pipe 82 enters the swirlchamber 20 from beneath the swirl chamber and is routed upwardly throughthe orifice 24, the ceiling 28 and above the liquid collection tray 78.The quench feed pipe terminates in a nozzle (not shown) which is coveredby a deflector 82A. Any suitable nozzle and deflector may be used. Thisembodiment enables the quench fluid to be introduced above the swirlchamber, thereby forcing the quench fluid to come into close contactwith fluids from the upstream of the reactor and undergo efficientmixing with such fluids.

In another alternative embodiment (schematically illustrated in FIG.4E), the quench fluid may be introduced through a quench feed pipe 82routed horizontally below the swirl chamber 20, extending verticallythrough the central outlet orifice (or “central orifice”) 24, andterminating inside the swirl chamber. This alternative embodimentretains the above-mentioned advantage of reduced vertical height as thequench feed pipe utilizes the vertical height required by the webs 68 ofthe radial support beams.

In the embodiments of FIGS. 4D and 4E, the concentric manifold 84,quench laterals 86, and nozzles 88 are not required. It will beunderstood that FIGS. 4D and 4E are intended to illustrate schematicallythe concept of an alternative manner of introduction of the quenchfluid. Thus, in these figures not all of the details of the picturedportion of the device are illustrated.

As noted above, the swirl chamber has a floor 22 consisting of a solidplate that surrounds a central orifice 24. An overflow weir 26 about theperiphery of the orifice extends above the orifice to define a basin onthe floor inside the swirl chamber. At the center of the swirl chamber,the fluid overflows the weir and exits the swirl chamber.

The fluid exiting the swirl chamber is directed downward to the roughdistribution network 100 (best seen in FIGS. 4A, 5A, 5B, and 5C) whichcollects the swirl chamber exit fluid and directs it radially outwardand onto the distribution apparatus 120. The rough distribution networkincludes a splash plate 102 and channels 108 in fluid communication withthe splash plate. The splash plate is located below the swirl chamberoutlet weir and may be removably secured by a support 65 attached to thecentral hub 64 of the support structure. The splash plate has apertures104 to allow some of the fluid to pass through and onto theredistribution plate 122. The splash plate also has shallow sides 106except possibly where it intersects with the channels 108. At theseintersections, the shallow sides preferably have openings connecting thesplash plate with the channels to ease the fluid passage. Fluidaccumulating on the splash plate will flow into the channels andradially outward into the vessel.

In an alternative embodiment, the shallow sides 106 of the splash plate102 may be omitted, provided that proper sealing between the splashplate 102 and the support 65 is achieved to minimize fluid leakage.

The channels 108 are in communication with the splash plate and extendradially outward toward the vessel wall. Preferably, the channels areattached to the webs 68 of the first set of radial support beams (wheretwo sets are provided). The channels have shallow sides 110 that providea conduit for fluid to flow toward the reactor wall. The channels,however, may have any shape suitable for collecting the fluid anddistributing it across the surface of the redistribution tray. Forexample, the channels may be substantially U-shaped, with either a flathorizontal bottom or a rounded bottom, or may be V-shaped. At intervalsalone the channels, notches 112 are provided in the sides to produce thedesired distribution of fluid onto the redistribution plate. Preferably,the shape and location of the notches provides a symmetrical dispersionof the fluid across the surface of the redistribution plate.

Below the splash plate is the distribution apparatus 120. Thedistribution apparatus may be fastened to the first set of radial beams(where two sets are provided) by for example, supporting it on thebottom flange of the first set of radial beams and fastening, ifdesired, by any suitable means to the bottom flange of the radial beams.As shown in FIGS. 6A and 6B, the distribution apparatus includes aredistribution plate 122 with a plurality of apertures 124, a pluralityof bubble caps 130, and a plurality of associated drip trays 150.Preferably, the redistribution plate fills substantially the entirecross section of the vessel and is oriented substantially horizontal toprovide a substantially level area to collect the fluid from the roughdistribution network. The apertures 124 in the plate are preferablysymmetrically distributed to achieve a symmetrical distribution of fluidacross the catalyst surface.

FIGS. 6A and 6B show bubble caps associated with the apertures of theredistribution plate. Preferably, an individual bubble cap is associatedwith, e.g., located above, an individual aperture to providesubstantially the sole means for fluid to pass through theredistribution plate. In this preferred embodiment, the redistributionplate is sealed to prevent the fluids from bypassing the bubble caps.Since the plate apertures are symmetrically distributed, the bubble capsare likewise symmetrically distributed. It is to be understood, however,that many other arrangements may be suitable.

Generally, one of the design considerations for the tray is that therebe a sufficient number of bubble caps to ensure substantially uniformliquid distribution over the entire surface of the plate. The optimumnumber of bubble caps for any given purpose will depend upon manyfactors, the most obvious being the size of the reactor. Othercontributing factors may be the liquid and gas flow rate to the reactorand the proportion of the feed remaining in the liquid phase. Ingeneral, the design of the redistribution plate will provide the propernumber of bubble caps to assure acceptable liquid distribution andestablish optimum liquid level on the upper surface of the tray andconcomitant optimization of gas flow through each bubble cap for a givenfeed rate and reactor size.

The bubble caps 130 include a riser 132 and a spaced apart cap 140 toform an inverted U-shaped flow path for the gas and liquid. The riser,which is generally cylindrical in form, has a lower lip 134 or extensionthat is received within an aperture in the plate 122, and a top 138. Theriser may be cut from a length of tubular material or may be rolled froma length of sheet stock as desired. The riser is secured to theredistribution plate by, for example, metal rolling or welding, or someother similar and suitable means. The riser has an inner passageway 136between the lower lip and the top that provides a means of fluidcommunication across the redistribution plate. In one of the preferredembodiments where an individual bubble cap is associated with anindividual aperture, the inner passageway of the riser providessubstantially the sole means of fluid communication across theredistribution plate.

The cap 140 encompasses the top of the riser but is spaced from theriser to define a bubble cap annulus (or annular space). The capcomprises a top wall 142 terminating about its periphery in a downwardlyextending skirt 144 that terminates above the upper surface of theredistribution plate and forms a gap between the skirt and the uppersurface of the redistribution plate. Preferably, the cap has a pluralityof slots 146 in its lowermost outer periphery such as shown in U.S. Pat.No. 3,218,249, incorporated herein by reference. The slots allow the gasor vapor to flow into the annulus. The slots also provide a pressuredrop such that the liquid level in the annular space defined by the capand the riser is higher than the liquid level on the redistributionplate. The higher liquid level in the annular space will tend to offsetany irregularities in the liquid level on the redistribution plate andensure a substantially uniform gas-liquid flow through each bubble cap,and substantially uniform mixing of the gas and liquid.

At least one spacer 148 is located intermediate to the riser and the capto maintain the two in a spaced apart relationship with one another. Thespacer or spacers may also be arranged so that the riser and the cap aremaintained in a concentric relationship to each other. The spacer may befastened to the riser, the cap, or both so that the top wall of the caprests on the spacer. Preferably, the spacers extend radially outward tomaintain the cap substantially centered with respect to the riser.

The bubble cap design promotes uniform liquid distribution even when thetray is not perfectly level or when there are differences in liquiddepth across the tray. In addition, the liquid and gas phases are moreintimately contacted compared to a chimney type distributor. Thisincreases the level of thermal equilibration of the reactants.

In operation, the liquid phase, substantially disengaged from the vapor(or gas) phase by gravity as it falls from the rough distributionnetwork, fills up on the redistribution plate to a level below the slotdepth in the bubble caps, with the level being determined primarily bythe gas flow rate per cap. It is, of course, necessary that some of theslot openings be exposed above the liquid surface to permit the gas topass through.

The pressure drop through the redistribution tray in the reactor, whichis normally quite small, forces the gas under the cap, either throughthe slots or under the cap. The gas entrains the liquid that is presenton the surface of the tray as it passes through the slots or under thecap. The fluid (gas and liquid) then flows upwardly through the annulusbetween the cap and the riser, reverses direction and flows through thepassageway defined by the riser. The bottom of the riser extends throughthe aperture in the plate to provide a drip edge for liquiddisengagement.

Although bubble caps may satisfactorily distribute the fluid across thecatalyst surface, the present invention contemplates increasing thenumber of fluid drip streams exiting the redistribution plate to furtherenhance the symmetrical distribution of the fluid across the catalystsurface. Consequently, in one embodiment, the present inventioncontemplates providing at least some horizontal drip trays 150associated with at least some bubble caps and located underneath theassociated bubble caps. An individual drip tray may be associated withand located directly underneath an individual bubble cap to collect theliquid from that cap and distribute it in a more finely divided and evenmore symmetrical pattern than can be achieved without the drip tray.

The drip tray 150 is constructed with a bottom 152 and a plurality ofside walls 154 extending upward from the bottom. The bottom has at leastone discharge port 156 and, preferably has at least two discharge portsto effectively multiply the number of drip streams. As shown in FIG. 6B,the bottom of the drip tray has a plurality of discharge ports disposedrelatively close to the corners to evenly discharge the liquid from thedrip tray. It is to be recognized, however, that a variety of methods ordevices may be suitable to accomplish the objective of multiplying thenumber of drip streams.

The drip tray is secured to the redistribution plate by, for example,welding. FIG. 6B shows mounting tabs 158 extending upward from the driptray to be secured to the underside of the redistribution plate. Ofcourse, any other suitable attachment methods can be used. The drip trayis spaced from the bottom opening of the riser and is oriented in ahorizontal manner. The horizontal positioning of the drip tray (ortrays) permits the liquid traveling downward to accumulate within thedrip tray and then be discharged from the tray in at least one, andpreferably in more than one, stream through the discharge ports.Preferably, the drip tray is spaced a distance of about 1 to 2 inchesfrom the redistribution plate.

Referring now to FIG. 7, there is shown an alternative embodiment of adrip tray 200 having drip guides. The drip tray 200 is shown with thedrip guides 202 placed at each corner 204 to protect and guide thedischarged liquid falling from the discharge ports 206 formed in thebottom 207 of the drip tray.

Another embodiment of the drip tray is shown in FIG. 8. In thisembodiment, a drip tray 210 is constructed with side walls 211surrounding a bottom surface 212. A plurality of discharge ports 216 arepositioned relatively close to the corners 218 of the drip tray. Thebottom of the drip tray also has a number of indentations 220 to form apattern of flow channels leading outwardly to the discharge ports and tofurther enhance the equal distribution of the liquid through thedischarge ports. V-shaped notches 222 may be provided at the corners ofthe top of the side walls to accommodate overflow from the drip tray inthe event of high liquid flow rates.

In yet another alternative embodiment of the drip tray, FIG. 9 shows adrip tray 230 having an x-shape. In this embodiment, the drip tray 230is constructed with four arms 231 each having side wall portions 232 todefine a controlled flow area. A discharge port 234 is provided at theend of each corner of the drip tray for the discharge of the collectedliquid.

While various alternative shapes of drip trays have been illustrated,one skilled in the art will appreciate that any shape suitable forcollecting and distributing liquid through a multiplicity of dischargepoints (or ports) may be used. One skilled in the art will alsounderstand that modifications may be made to the drip tray to achievesymmetry and flow balance as necessary to meet the desired performanceparameters for a particular reaction vessel. The drip trays willtherefore more finely divide the liquid stream entering the catalyst bedbelow.

It will be appreciated that the bubble cap design described aboveprovides substantially uniform liquid distribution even when theredistribution plate is not perfectly level or when there aredifferences in the depth of the liquid across the surface of the plate.In addition, the liquid and gas phases will be more intimatelycontacted, especially as compared to prior art chimney typedistributors. Consequently, the level of thermal equilibration of thereactants, i.e., the gas and liquid, is increased.

In an alternative embodiment, instead of a drip tray, a deflector bafflemay be attached just below the outlet of the riser inner passageway 336.(FIGS. 10, 11 and 12). The bubble cap illustrated in FIGS. 10 and 11(and FIGS. 13, 16-19, discussed below) has a somewhat different designfrom the bubble cap of FIG. 6B. Nonetheless, the modifications of thebubble caps discussed in connection with the design of FIGS. 10, 11, 13and 16-19, are equally applicable to the bubble cap design of FIG. 6B.The bubble cap illustrated in FIGS. 10, 11, 13 and 16-19 is of aconstruction known in the art. Ballard et al., U.S. Pat. No. 3,218,249,Treese, U.S. Pat. No. 5,045,247 and Shih et al., U.S. Pat. No.5,158,714, incorporated herein by reference, disclose bubble caps ofsuch design. In FIGS. 10, 11, 13 and 16-19, whenever appropriate,various elements are labeled with reference numerals having the samelast two digits as the corresponding elements in the preceding Figures.For example, the plate 322 of FIG. 10 corresponds to the plate 122 ofFIG. 6A. The basic design of the bubble cap of FIGS. 10, 11 (and, thus,13, 16-19) is conventional in the art (other than the modifications ofthis invention) and is only summarized herein. The bubble cap of thesefigures includes a skirt 344, a spacer 348, and a riser 332 (FIG. 10).An annular space is formed between the skirt and the riser. The lowerlip 334 of the riser and the outer edge of the deflector baffle 301define a riser outlet distribution orifice 303 (FIG. 12). The arrows inFIG. 12 show the direction of flow of fluid from the riser outletdistribution orifice. The deflector baffle may take various shapes,including as examples: a substantially flat, solid, round disc (FIGS. 10and 11), a frusto-conically shaped disk or a cone with its apex pointingupward toward the outlet of the riser inner passageway 336. The cone mayhave apertures in its side surface. Examples of suitable deflectorbaffles are illustrated in FIGS. 10 and 13-15. An inverted,conically-shaped deflector baffle 301C is illustrated in FIG. 13. FIG.14 shows the top view of a substantially flat, solid deflector bafflewith openings 350. FIG. 15 is a top view of a deflector baffle havingthe shape of a substantially flat disc with slots 600, and an opening601.

The cross-section of the deflector baffle may have any suitable shape,e.g., circular (or round) or pyramidal. If the deflector baffle ispyramidal, it would be preferably placed under the outlet of the riserinner passageway, so that the apex of the pyramid faces into thepassageway (similarly as shown in FIG. 13 for the cone-shaped deflectorbaffle). In one preferred embodiment, the cross-section of the deflectorbaffle is circular (FIGS. 10-11). The deflector baffles may be attachedjust below the outlet of the riser inner passageway in any suitablemanner. One way of attaching a deflector baffle is illustrated in FIGS.10 and 13. In FIGS. 10 and 13, the defector baffle is attached to alower lip 334 by an attachment means, such as a crossbar 320.

The distance between the outlet of the riser inner passageway and adeflector baffle may vary, depending on a variety of factors, such asprocess design, and may be determined by those skilled in the art.

In contrast to the drip tray 210, however, the primary intent (orfunction) of the deflector baffle is to redirect the majority of thedownflowing fluid from its principally vertically downward path, as arelatively narrow stream through the middle of the riser outletdistribution orifice (as is often the case with risers without adeflector baffle). With a deflector baffle, the fluid is distributed ina pattern over a wider area of the catalyst bed below. Preferably, thespray patterns emanating from adjacent deflector baffles would overlap,providing a substantially uniform fluid coverage over the catalyst bed.This can be accomplished by various means, e.g., by adjusting velocityof the fluid flow through the distribution orifice 303.

The present invention also contemplates yet another alternative means ofincreasing the number of fluid drip streams exiting the redistributionplate to further enhance the symmetrical distribution of the fluidacross the catalyst surface. Consequently, in a preferred embodiment,the present invention contemplates providing a plurality of riser vanesassociated with (or included in) at least some bubble caps and locatedbetween the top 438 of the riser 432 and the underside of bubble cap topwall 442 (FIGS. 16, 17). Preferably, an individual set of riser vanes460 is associated with and directly attached concentrically to the topof an individual riser 432. Preferably, the top edge of the riser vanesshould be flush against the underside of the bubble cap top wall 442, toprevent the passage of fluid between the bubble cap top wall 442 and theriser vanes. The riser vanes are spaced apart from one another (FIG.17), defining therebetween vane passageways 461 for fluid communicationbetween the bubble cap annulus and the riser inner passageway 436, withsaid vane passageways being preferably the sole means of fluidcommunication between the bubble cap annulus and the riser innerpassageway. At least one spacer 448 is located between the riser and thecap to maintain these two elements spaced from each other. The spacer orspacers may also be arranged so that the riser and the cap aremaintained concentrically to each other. The spacer may be fastened tothe riser, the cap, or both so that the top wall of the cap rests on thespacer. Preferably, the spacer(s) extend radially outward to keep thecap substantially centered relative to the riser.

In operation, liquid (and vapor) entering the vane passageways from thebubble cap annulus will be directed circumferentially about the innerwall of the riser 432. In contrast, without the vanes, the liquid (andvapor) would be likely to randomly flow down, usually through the centerof the riser inner passageway 436. The circumferential flow path of theliquid (and vapor) results in a more uniform wetting of the inner wallof the riser 432, and hence a more uniform distribution of the liquid asit falls from a lower lip 434 of the riser (similar to the lip 134 inFIG. 6B). It is further believed that the riser vanes, when used inconjunction with the deflector baffles discussed previously, willproduce a significant improvement in the uniformity of the distributionof the fluids to the catalyst bed below.

The riser vanes may be flat, curved in shape or cut at an angle and maybe formed from the same tubular material or rolled sheet stock as theriser 432. FIGS. 18 and 19 illustrate an embodiment with the riser vanes560 cut at an angle. Also, in this embodiment, notches 562 formed in thelower lip 534 of the riser can aid in a more uniform distribution of theliquid exiting the riser inner passageway. In a preferred embodiment,the riser vanes are integral to the riser, being formed by machining andbending the uppermost portion of the tubular material from which theriser is formed.

While the present invention has been described with reference toproviding a unique quench zone mixing device that includes a swirlchamber, a rough distribution network, and a distribution apparatus, thepresent invention also contemplates an improvement in known quench zonemixing devices. In particular, a rough distribution network isinterposed between a mixing chamber and a distribution apparatus. Therough distribution network includes a splash plate in fluidcommunication with outwardly extending channels. Preferably, thechannels extend outward radially from the splash plate.

The splash plate is located below the exit opening or openings of themixing chamber and collects the fluid (e.g., a liquid) from the mixingchamber. The splash plate may have shallow sides except possibly whereit intersects with the channels. Fluid accumulating on the splash platewill flow into the channels and radially outward. The splash platepreferably has a few apertures and the channels preferably include sidewalls with spaced apart notches to allow fluid to exit the channels.Preferably, the shape and location of the notches provides a symmetricaldispersion of the fluid across the surface of the distributionapparatus.

In addition, the present invention relates to the above-describeddistribution apparatus which is not associated with the quench zonemixing apparatus. For example, as shown in FIG. 1, the distributionapparatus 120 may be provided near the top of the reactor. In thisembodiment, the distribution apparatus will collect fluid from above,evenly distribute it across the top surface of the redistribution plate,and further distribute the fluid downward to a down stream section ofthe reactor. While the distribution apparatus has been shown as beinglocated near the top of the reactor, one skilled in the art willappreciate that the apparatus may be suitably located where needed inthe reactor.

The present invention also contemplates using the above-describedembodiments of the quench zone mixing device in a process for contactinga fluid with a gas or liquid. Preferably, the process occurs in aportion of a reactor between two successive spaced apart beds ofparticle form solids, e.g., catalyst particles. The process includespassing the fluid with a gas through the quench zone mixing device ofthis invention, which is placed between the two successive beds.

In another embodiment, the process includes introducing a fluid into aplurality of inlet openings provided on a swirl chamber. The swirlchamber includes a wall disposed between a ceiling and a floor whichincludes an orifice that provides a means of fluid communication out ofthe swirl chamber. The wall defines an inside of the swirl chamber. Thefluid is mixed with a quench fluid that is also introduced into theswirl chamber to produce a swirl chamber fluid mixture. The swirlchamber fluid mixture is transported out of the swirl chamber and iscollected on a rough distribution network disposed beneath the swirlchamber. The rough distribution network includes a splash plate andoutwardly extending channels, wherein the splash plate is adapted tocollect the swirl chamber fluid mixture and radially distribute itthrough the channels and onto a distribution apparatus disposed beneaththe rough distribution network. The distribution apparatus includes aredistribution plate having a plurality of apertures and a plurality ofbubble caps with at least some of the bubble caps associated with atleast some of the apertures and collects the swirl chamber fluidmixture. The collected swirl chamber fluid mixture is transportedthrough the redistribution plate via the apertures and the bubble caps.

In one embodiment, a plurality of substantially horizontal drip traysare provided with at least some of the drip trays located underneath theredistribution plate and associated with at least some of the bubblecaps, wherein the drip trays receive the fluid exiting the bubble capsand distribute it through at least one discharge port in the drip trays.If gas is present in the fluid, at least some separation of the gas fromthe fluid takes place in the bubble caps and on the drip trays.

As noted throughout, the embodiments described above provide a number ofsignificant advantages. Importantly, the overall pressure drop acrossthe device is expected to be low while achieving excellent mixing anddistribution of the gas and liquid.

By providing a fluid (e.g., liquid) collection tray that is sloped, theresidence time of the liquid on the tray is minimized which reducesthermal cracking of the liquid and in certain processes reduces cokingand the formation of precursors of polynuclear aromatics.

The presence of spaced apart inlet openings on the side wall of theswirl chamber reduces the overall vertical height of the quench zonemixing apparatus. In addition, by providing side inlet openings, thequench fluid can also be introduced into the side of the swirl chamberwhich also aids in minimizing the overall vertical height of theapparatus. As a result, the height of the reactor vessel can be reduced,thereby reducing the capital cost of the reactor vessel.

Where baffles are provided, the fluid is directed downwardly andcircumferentially and can be intimately contacted by the quench fluidthat is introduced into the side of the swirl chamber to provide anefficient mixing and equilibration of the two fluids. Moreover, bycreating a swirling flow of both, the fluids from the multiple inletopenings and the quench fluid, an intimate mixing of fluids from allsections of the vessel can be achieved that will minimize hot zonepropagation from one catalyst bed to the next.

In the preferred embodiment where the baffles are attached to the insideof the swirl chamber, there will be no need to remove the baffles duringmaintenance. Consequently, the swirl chamber can be easily maintained.

As pointed out above, in a preferred embodiment the rough distributionnetwork includes channels that are attached to the radial beams. Thechannels will not obstruct access to the redistribution tray from aboveand will, therefore, facilitate maintenance when cleaning of theredistribution tray is required. In addition, the number of individualpieces required is reduced which, in turn, reduces the capital cost,assembly time and maintenance cost.

By including the support structure as described above, the reactordesign and fabrication will be simplified since multiple support ringsor internal skirts will be dispensed with. Moreover, by dispensing withan internal skirt, the entire interior surface of the reactor will beavailable for inspection.

In one embodiment, drip trays are used with each bubble cap on theredistribution tray. The bubble caps provide good distribution of gasand liquid over the cross sectional surface below the redistributiontray. The drip trays improve the liquid distribution by multiplying theliquid distribution points. The drip trays can also extend under fixedinternals such as beams or wall support rings to wet areas that couldnot be reached by the normal bubble cap or by a chimney typedistribution device.

In another preferred embodiment, a deflector baffle is utilized tosubstantially prevent the flow of fluid in a relatively narrow streamsubstantially through the middle of the cross-section of the riser. Thedeflector baffle provides a substantially uniform distribution of thefluid in a pattern over a wider area of the catalyst bed below.

In yet another preferred embodiment a plurality of riser vanes includedin at least one of the bubble caps, between the top of the riser and theunderside of a bubble cap top wall, define vane passageways. The vanepassageways cause the fluids (liquid and vapor) to be directedcircumferentially about the inner wall of the riser, thereby promoting amore uniform distribution of the liquid as it exits the riser.

Viewed from another perspective, the present application discloses aninterzone mixing apparatus comprising: a swirl chamber having a liquidcollection tray upon which a material swirls; a distribution apparatushaving a plurality of bubble caps each of which includes a riser vane;and a rough distribution network interposed between the swirl chamberand the distribution apparatus. In preferred embodiments the liquidcollection tray includes a plurality of floor obstacles that inducelocal tubulence in the material as it swirls, with such floor obstacleshaving suitable shapes such as ridged sloped panels or flat, “V”,scalloped or “U” shaped tray baffles. the floor obstacles mayadvantageously be integrated into the liquid collection tray. The bubblecaps preferably include a plurality of the riser vanes, which mayadvantageously be interposed between the riser portion and the capportion of the corresponding bubble caps. It is especially preferredthat the riser vanes, which are preferably flat, curved, or cut at anangle, are spaced from each other to define vane passageways.

It should be understood that a wide range of changes and modificationscan be made to the embodiments described above. It is therefore intendedthat the foregoing description illustrates rather than limits thisinvention, and that it is the following claims, including allequivalents, which define this invention.

1. A mixing apparatus comprising: a swirl chamber having an outlet; adistribution network in fluid communication with, and downstream of theoutlet, having a plurality of fluid guides extending outwardly relativeto the outlet, and a plurality of bubble caps having a plurality ofriser vanes; and wherein the outlet and the fluid guides are disposed ina hub and spoke configuration.
 2. The mixing apparatus of claim 1 inwhich the swirl chamber is disposed to receive a material from aplurality of openings, each of which is fitted with a member that atleast partially directs the material in a swirling motion.
 3. The mixingapparatus of claim 1 in which the swirl chamber is disposed to receive amaterial from a plurality of openings, each of which is fitted with aramp sloping downward in a direction of flow into the swirl chamber. 4.The mixing apparatus of claim 1 in which the swirl chamber is fittedwith a plurality of wall baffles.
 5. The mixing apparatus of claim 1further comprising a collection tray having a plurality of floor bafflesupstream of the plurality of openings.
 6. The mixing apparatus of claim1 further comprising a pipe that feeds a quench material into the swirlchamber.
 7. The mixing apparatus of claim 1 wherein each of theplurality of bubble caps further includes a riser and a cap, positionedsuch that the riser vanes are located between the riser and the cap. 8.The mixing apparatus of claim 1 wherein the plurality of riser vanes arespaced apart from each other to define a plurality of vane passageways.9. The mixing apparatus of claim 1 wherein the riser vanes are flat,curved, or cut at an angle.
 10. The mixing apparatus of claim 1 in whichthe swirl chamber has a wall that includes a plurality of openings thatreceive a material and impart a swirling force to the material, and aramp sloping downward in a direction of flow into the swirl chamber. 11.The mixing apparatus of claim 10 in which the wall is fitted with aplurality of wall baffles, and further comprising a collection trayhaving a plurality of floor baffles fluidly communicating with, andupstream of the plurality of openings.
 12. The mixing apparatus of claim1 wherein the fluid guides are also radial support beams that supportthe swirl chamber.
 13. The mixing apparatus of claim 1 furthercomprising a splash plate fluidly interposed between the outlet of theswirl chamber and the distribution network.
 14. A multizoned vesselhaving a mixing apparatus according to claim 1 fluidly interposedbetween a first reaction zone and a second reaction zone.